Sheet-like waterproofing membranes are well-known for application to concrete and other building and construction substrates, such as roofs and foundations. These waterproofing membranes typically are laminates that comprise a carrier sheet and a pressure sensitive adhesive layer. The pressure sensitive adhesive layer is typically made of rubber modified asphalt (bitumen). The membranes also typically include a removable release sheet that is used to prevent the adhesive portion of the membrane from adhering to the carrier sheet or other portion of the membrane when the membrane is rolled up. This release sheet must be removed from the membrane prior to or during installation.
Although there are numerous varieties of waterproofing membranes disclosed in the art, it has been difficult to produce a waterproofing membrane that exhibits good performance characteristics at both high and low temperatures. Ideal performance characteristics for the pressure sensitive adhesive include resistance to flow at temperatures up to 240° F. (116° C.) without the need for internal reinforcement of the adhesive; good adhesion over a broad temperature range; resistance to cracking at temperatures as low as −20° F. (−29° C.); and low viscosity at mixing and coating temperatures (typically about 300-375° F. or about 149-191° C.) for easy manufacturing.
Bitumen itself does not exhibit pressure sensitive adhesive characteristics, is brittle at low temperatures and exhibits excessive flow at high temperatures. Typically, elastomers, such as SBS, SBR, SIS, and SEBS, are blended with bitumen to produce pressure sensitive adhesive characteristics, and to provide flexibility at low temperatures and resistance to flow at high temperatures. In addition, a plasticizer such as a petroleum oil may also be required. However, use of elastomers alone does not produce the desired performance at both high and low temperatures. Often, one performance characteristic is sacrificed to obtain another.
Thermoplastics such as high density polyethylene, low density polyethylene, ethylene vinyl acetate (EVA), atactic polypropylene (APP), and polypropylene have been used for bitumen modification. However, thermoplastics are generally less compatible with bitumen than the elastomers previously described and blends of thermoplastics and bitumen generally do not exhibit pressure sensitive characteristics. Depending on the thermoplastic(s) used, high temperature flow resistance and/or low temperature flexibility may be improved or negatively affected. U.S. Pat. No. 7,317,045 describes a modified bitumen composition comprising a blend of asphalt and polyethylene, where the polyethylene is a mixture of high density polyethylene (HDPE) and low density polyethylene (LDPE).
Recycled vulcanized elastomers such as ground tire scrap also have been added to bitumen compositions. These additives generally behave like inert fillers and only minimally impact high temperature flow resistance and low temperature flexibility. See, for example, U.S. Pat. Nos. 3,644,420, 5,558,703, CN 101205393 and CN 101205396.
It is an object of the present invention to provide a waterproofing membrane with improved high and low temperature performance characteristics.